Shim support guide jig for magnetic field generation apparatus, magnetic field generation apparatus and magnetic resonance imaging equipment each including shim support in which magnetic material shims are arranged and adjusted by employing shim support guide jig, and magnetic field adjustment method for magnetic field generation apparatus, as well as magnetic field adjustment method for magnetic resonance imaging equipment

ABSTRACT

A shim support guide jig includes a shim support guide pipe in which a guide passage for guiding the movement of a shim support is formed. In a state where a superconducting magnet has generated a static magnetic field, the designated shim support can be drawn out from the internal space of the superconducting magnet through the guide passage, and the designated shim support for which magnetic material shims have been arranged and adjusted can be inserted into the internal space through the guide passage. A magnetic field generation apparatus has the magnetic material shims arranged and adjusted using the shim support guide jig, and a magnetic resonance imaging equipment employs the magnetic field generation apparatus. Magnetic field adjustment methods for the magnetic field generation apparatus and for the magnetic resonance imaging equipment are performed using the shim support guide jig.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a shim support guide jig for a magnetic fieldgeneration apparatus, a magnetic field generation apparatus and amagnetic resonance imaging equipment each including a shim support inwhich magnetic material shims are arranged and adjusted by employing ashim support guide jig, and a magnetic field adjustment method for amagnetic field generation apparatus, as well as a magnetic fieldadjustment method for a magnetic resonance imaging equipment.

2. Description of the Related Art

A magnetic field generation apparatus including a superconducting magnetis used in a magnetic resonance imaging equipment. The superconductingmagnet is configured in a cylindrical shape, and it generates a staticmagnetic field in its internal space. A patient is arranged in thestatic magnetic field, and the image diagnosis of the patient is made.

A magnetic field whose magnetic field strength is high, which has auniform magnetic field strength in the internal space, and which is ofhigh temporal stability, is required of the static magnetic field. Thesuperconducting magnet is used for generating such a static magneticfield. Concretely, it is required of the superconducting magnet for themagnetic resonance imaging equipment to generate a magnetic field whichhas a very uniform magnetic field strength of, for example, within 3ppm, in a magnetic field space near the center of the magnetic field.Therefore, the superconducting magnet is designed at a high precision incorrespondence with the requirement. In actuality, however, theuniformity of the magnetic field in the magnetic field space lowers dueto a manufacturing dimensional error in a process for producing thesuperconducting magnet, the influence of a magnetic material existingaround a place where the superconducting magnet is installed, and soforth.

For this reason, the superconducting magnet is additionally providedwith a magnetic field adjustment device for making the fine adjustmentof the magnetic field strength. The magnetic field adjustment deviceemploys magnetic material shims made of a magnetic material of, forexample, high permeability. The magnetic material shims serve to correctthe disorder of the magnetic field strength of the static magnetic fieldgenerated by the superconducting magnet, and they are arranged andadjusted on the basis of the distribution evaluation of the magneticfield strength. More specifically, the magnetic material shims have adesignative volume which is designated on the basis of the distributionevaluation of the magnetic field strength, and they are arranged at adesignative position which is designated on the basis of thedistribution evaluation. The disorder of the static magnetic fieldgenerated by the superconducting magnet is corrected with a magneticfield which is generated by the magnetization of the magnetic materialshims, whereby a highly uniform magnetic field is obtained. Regardingthe magnetic material shims, Patent Documents 1 (JP63-122441A,especially FIGS. 1 and 2 and their explanations), 2 (JP5-220127A,especially FIG. 2 and its explanation), and 3 (JP5-329128A) have beenknown.

FIGS. 1 and 2 of Patent Document 1 disclose a magnetic field strengthcorrection device wherein a pair of protrusions are formed through leafsprings on both the sides of a holder for holding the magnetic materialshims, and the holder is arranged at the predetermined position of aholding member by using the protrusions. Besides, FIG. 2 of PatentDocument 2 discloses a magnet device wherein a slide plate is disposedbetween a pair of groove-shaped members, and the magnetic material shimsare arranged on the slide plate, whereby the mounting position of themagnetic material shims can be freely set. Further, Patent Document 3discloses a magnetic field correction device wherein a plurality of flatmagnetic material members which are equal in length, thickness and widthare formed with holes, so as to output a desired magnetic fieldcorrection component.

The techniques of Patent Documents 1 and 2 serve to set the mountingposition of the magnetic material shims, and the technique of PatentDocument 3 serves to adjust the magnetic field correction component ofthe magnetic material shims. In general, in a state where thesuperconducting magnet is excited to generate the static magnetic field,an intense electromagnetic force acts on the magnetic material shims,and hence, the magnetic material shims cannot be safely arranged andadjusted. Accordingly, the adjustment of the position of the magneticmaterial shims according to Patent Document 1 or 2 and the adjustment ofthe volume of the magnetic material according to Patent Document 3 aremade in a state where the superconducting magnet is once deexcited.Thereafter, the superconducting magnet needs to be excited again forconfirming the magnetic field strength. However, a long time, forexample, about one hour is expended on each of the excitation anddeexcitation of the superconducting magnet, and a time period of twohours or more is required for deexciting the superconducting magnet onceand exciting it again. As another problem, in deexciting and excitingthe superconducting magnet, large currents must be caused to flowthrough current leads made of a normal conductor. Joule heat isgenerated within the superconducting magnet by the large currents, andliquid helium is vaporized and decreased by the Joule heat.

SUMMARY OF THE INVENTION

This invention proposes a shim support guide jig for a magnetic fieldgeneration apparatus as can draw magnetic material shims out of themagnetic field generation apparatus and insert them thereinto in a statewhere a superconducting magnet generates a magnetic field.

Also, this invention proposes a magnetic field generation apparatuswhose magnetic field strength can be adjusted using a shim support guidejig, in a state where a superconducting magnet generates a magneticfield.

Besides, this invention proposes a magnetic resonance imaging equipmentwhich includes the magnetic field generation apparatus.

In addition, this invention proposes a magnetic field adjustment methodfor a magnetic field generation apparatus as adjusts the magnetic fieldof the magnetic field generation apparatus, in a state where asuperconducting magnet generates a magnetic field.

Further, this invention proposes a magnetic field adjustment method fora magnetic resonance imaging equipment as employs the magnetic fieldadjustment method for the magnetic field generation apparatus.

A shim support guide jig for a magnetic field generation apparatusaccording to this invention concerns a shim support guide jig for amagnetic field generation apparatus including a superconducting magnetwhich is configured in the shape of a cylinder and which generates amagnetic field in its internal space, and a plurality of shim supportswhich are arranged in the internal space and which serve to accommodatetherein magnetic material shims for adjusting a magnetic field strengthof the magnetic field. The shim support guide jig includes a shimsupport guide pipe in which a guide passage for guiding a movement ofthe shim support is formed. Thus, the shim support designated among theplurality of shim supports is drawn out from the internal space throughthe guide passage, and the designated shim support is inserted into theinternal space through the guide passage.

Besides, a magnetic field generation apparatus according to thisinvention includes a superconducting magnet which is configured in theshape of a cylinder and which generates a magnetic field in its internalspace, and a plurality of shim supports which are arranged in theinternal space and which serve to accommodate therein magnetic materialshims for adjusting a magnetic field strength of the magnetic field.Here, the shim support designated among the plurality of shim supportshas had the magnetic material shims arranged and adjusted in a statewhere it has been drawn out from the internal space via a guide passageformed in a shim support guide pipe of a shim support guide jig, and ithas been thereafter inserted into the internal space via the guidepassage.

Besides, a magnetic resonance imaging equipment according to thisinvention includes the magnetic field generation apparatus according tothis invention, and it makes the magnetic resonance imaging diagnosis ofa patient arranged in the internal space.

Besides, a magnetic field adjustment method for a magnetic fieldgeneration apparatus according to this invention concerns a magneticfield adjustment method for a magnetic field generation apparatusincluding a superconducting magnet which is configured in the shape of acylinder and which generates a magnetic field in its internal space, anda plurality of shim supports which are arranged in the internal spaceand which serve to accommodate therein magnetic material shims foradjusting a magnetic field strength of the magnetic field. The magneticfield adjustment method here includes drawing out at least one shimsupport designated among the plurality of shim supports, from theinternal space via a guide passage formed in a shim support guide pipeof a shim support guide jig; accommodating the magnetic material shimsof designative volume at a designative position of the designated shimsupport; and inserting the designated shim support in which the magneticmaterial shims have been accommodated, into the internal space via theguide passage.

Further, a magnetic field adjustment method for a magnetic resonanceimaging equipment according to this invention concerns a magnetic fieldadjustment method for a magnetic resonance imaging equipment which makesthe magnetic resonance imaging diagnosis of a patient arranged in theinternal space. The magnetic field adjustment method here employs themagnetic field adjustment method for the magnetic field generationapparatus according to this invention.

Owing to the use of the shim support guide jig according to thisinvention, in the state where the superconducting magnet has generatedthe magnetic field in the internal space, it is possible to draw out thedesignated shim support from the internal space to a place where theinfluence of the magnetic field becomes little, to perform thearrangement and adjustment of the magnetic material shims for thedesignated shim support in the place, and to insert the designated shimsupport into the internal space. Therefore, in the state where thesuperconducting magnet has generated the static magnetic field, thearrangement and adjustment of the magnetic material shims can beperformed, and a time period required for the magnetic field adjustmentcan be shortened. Moreover, in the arrangement and adjustment of themagnetic material shims, the deexcitation and re-excitation of thesuperconducting magnet are dispensed with, and liquid helium can beprevented from decreasing due to its vaporization.

Besides, in the magnetic field generation apparatus according to thisinvention, at least one shim support designated among a plurality ofshim supports has had the magnetic material shims arranged and adjustedin a state where it has been drawn out from an internal space via aguide passage formed in a shim support guide pipe of a shim supportguide jig, and it has been thereafter inserted into the internal spacevia the guide passage. In a state where a superconducting magnet hasgenerated a static magnetic field, the arrangement and adjustment of themagnetic material shims are performed, and hence, a time period requiredfor a magnetic field adjustment is shortened. Moreover, in thearrangement and adjustment of the magnetic material shims, thedeexcitation and re-excitation of the superconducting magnet aredispensed with, and liquid helium can be prevented from decreasing dueto its vaporization.

Besides, the magnetic resonance imaging equipment according to thisinvention includes the magnetic field generation apparatus according tothis invention, and it makes the magnetic resonance imaging diagnosis ofa patient arranged in the internal space of a superconducting magnet.The magnetic field adjustment of the magnetic resonance imagingequipment can be performed in a state where the superconducting magnethas generated a magnetic field, and a time period required for amagnetic field adjustment can be shortened. Moreover, in the arrangementand adjustment of the magnetic material shims, the deexcitation andre-excitation of the superconducting magnet are dispensed with, andliquid helium can be prevented from decreasing due to its vaporization.

Besides, the magnetic field adjustment method for a magnetic fieldgeneration apparatus according to this invention includes drawing out atleast one shim support designated among the plurality of shim supports,from the internal space via a guide passage formed in a shim supportguide pipe of a shim support guide jig; accommodating the magneticmaterial shims of designative volume at a designative position of thedesignated shim support; and inserting the designated shim support inwhich the magnetic material shims have been accommodated, into theinternal space via the guide passage. According to the magnetic fieldadjustment method for the magnetic field generation apparatus, themagnetic field adjustment based on the magnetic material shims can beperformed in a state where a superconducting magnet has generated amagnetic field, and a time period required for a magnetic fieldadjustment can be shortened. Moreover, in the arrangement and adjustmentof the magnetic material shims, the deexcitation and re-excitation ofthe superconducting magnet are dispensed with, and liquid helium can beprevented from decreasing due to its vaporization.

Further, the magnetic field adjustment method for a magnetic resonanceimaging equipment according to this invention consists in a magneticfield adjustment method for a magnetic resonance imaging equipment whichmakes a magnetic resonance imaging diagnosis of a patient arranged in aninternal space of a superconducting magnet, wherein a magnetic fieldadjustment is performed by employing the magnetic field adjustmentmethod for the magnetic field generation apparatus according to thisinvention. According to the magnetic field adjustment method for themagnetic resonance imaging equipment, the arrangement and adjustment ofthe magnetic material shims can be performed in a state where thesuperconducting magnet has generated a magnetic field, and a time periodrequired for a magnetic field adjustment can be shortened. Moreover, inthe arrangement and adjustment of the magnetic material shims, thedeexcitation and re-excitation of the superconducting magnet aredispensed with, and liquid helium can be prevented from decreasing dueto its vaporization.

The foregoing and other objects, features, aspects and advantages ofthis invention will become more apparent from the following detaileddescription of this invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view, partly in section, showing a magneticfield adjustment state in Embodiment 1 of a magnetic resonance imagingequipment according to this invention;

FIG. 2 is a sectional view showing Embodiment 1 of a shim support guidejig according to this invention;

FIG. 3 is a perspective view showing the shim support guide jig and ashim support in Embodiment 1;

FIG. 4 is a sectional view showing a state where the shim support hasbeen drawn out by the shim support guide jig in Embodiment 1;

FIG. 5 is a sectional view showing Embodiment 2 of the shim supportguide jig according to this invention;

FIG. 6 is a sectional view showing Embodiment 3 of the shim supportguide jig according to this invention;

FIG. 7 is a perspective view showing the shim support guide jig and ashim support in Embodiment 3;

FIG. 8 is a sectional view showing Embodiment 4 of the shim supportguide jig according to this invention;

FIGS. 9( a) and 9(b) are a sectional view and a side view showingEmbodiment 5 of the shim support guide jig according to this invention,respectively; and

FIG. 10 is a perspective view showing a shim support which is used incombination with the shim support guide jig of Embodiment 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, several embodiments of this invention will be described withreference to the drawings.

Embodiment 1

FIG. 1 is a perspective view, partly in section, showing a magneticfield adjustment state in Embodiment 1 of a magnetic resonance imagingequipment according to this invention. FIG. 2 is a sectional viewshowing Embodiment 1 of a shim support guide jig according to thisinvention. FIG. 3 is a perspective view showing the shim support guidejig according to Embodiment 1 and a shim support. FIG. 4 is a sectionalview showing a state where the shim support has been drawn out by theshim support guide jig according to Embodiment 1.

A magnetic resonance imaging equipment 100 in Embodiment 1 as shown inFIG. 1 includes Embodiment 1 of a magnetic field generation apparatusaccording to this invention, and Embodiment 1 of a shim support guidejig according to this invention. The magnetic field generation apparatusin Embodiment 1 is indicated at numeral 10, and the shim support guidejig in Embodiment 1 is indicated at numeral 50.

As shown in FIG. 1, the magnetic field generation apparatus 10 includesa superconducting magnet 20, and a magnetic field adjustment device 30.The superconducting magnet 20 is configured substantially in the shapeof a cylinder, but it is partly cut away and is illustrated in FIG. 1for better understanding of its internal configuration. Thesuperconducting magnet 20 is configured in the cylindrical shape arounda center axis O-O, it has an internal space 21 inside, and it generatesa static magnetic field M in the internal space 21. A magnetic field ofhigh uniformity is required especially in a magnetic field space MCwhich is the central part of the static magnetic field M. The length ofthe internal space 21 in a direction parallel to the center axis O-O isdenoted by letter L.

Since the superconducting magnet 20 is well known, the structure thereofwill be briefly explained. The superconducting magnet 20 includes alow-temperature container 22 which is configured in the shape of acylinder. The low-temperature container 22 is configured of a heliumtank 23, a thermal shield tank 25 and a vacuum tank 26. The helium tank23 is configured in the shape of a cylinder, and a plurality ofsuperconducting coils 24 are accommodated in the helium tank 23,together with liquid helium. Each of the superconducting coils 24 isconfigured by winding a superconducting wire material whosesuperconductor is, for example, niobium titanate (NbTi), and the liquidhelium is accommodated as a coolant in order to hold the superconductingcoil 24 in a superconducting state. The thermal shield tank 25intercepts external heat invading into the helium tank 23, and it isconfigured in the shape of a cylinder so as to cover the outer surfaceof the helium tank 23. The vacuum tank 26 is configured in the shape ofa cylinder so as to further cover the outer surface of the thermalshield tank 25, and the interior thereof is held in a vacuum state.Incidentally, a refrigerator (not shown) is often connected to thelow-temperature container 22 in order to suppress the consumption of theliquid helium within the helium tank 23.

The magnetic field adjustment device 30 is arranged on the innerperipheral surface of the superconducting magnet 20, and it corrects themagnetic field strength of the static magnetic field M generated in theinternal space 21 by the superconducting magnet 20. This magnetic fieldadjustment device 30 includes a plurality of shim supports 31 arrangedon the inner peripheral surface of the superconducting magnet 20, andmagnetic material shims 40 necessary for the correction of the staticmagnetic field M. The magnetic material shims 40 are accommodated withineach of the shim supports 31 and are not shown in FIG. 1, but they willbe described with reference to FIG. 3 later.

The plurality of shim supports 31 are arranged on the inner peripheralsurface of the superconducting magnet 20. The respective shim supports31 are fixed at the predetermined positions (PP) of the inner peripheralsurface of the superconducting magnet 20 in parallel with the centeraxis O-O, and at equal peripheral intervals to one another. The length Lof each shim support 31 is substantially equal to the axial length L ofthe inner peripheral surface of the superconducting magnet 20. At thepredetermined positions (PP), the corresponding shim supports 31 lie intouch with the inner peripheral surface of the superconducting magnet 20over the full lengths L thereof. Each shim support 31 serves toaccommodate the magnetic material shims 40 for correcting the magneticfield strength of the static magnetic field M.

The distribution of magnetic field strengths in the magnetic field spaceMC is evaluated in a state where the superconducting magnet 20 hasgenerated the static magnetic field M. In order to correct the staticmagnetic field M, the arrangement of the magnetic material shims 40 isdetermined on the basis of the evaluation. Concretely, among theplurality of shim supports 31, at least one shim support 31 foraccommodating the magnetic material shims 40 therein is designated. Inaddition, a position for accommodating the magnetic material shims 40thereat, and the volume of the magnetic material shims 40 are designatedfor the designated shim support 31. The designated accommodationposition of the magnetic material shims 40 shall be called the“designative position (DP)”, and the designated volume of the magneticmaterial shims 40 shall be called the “designative volume (DV)”. In acase where two or more shim supports 31 for accommodating the magneticmaterial shims 40 therein are designated among the plurality of shimsupports 31, the designative positions (DP) are designated for therespective designated shim supports 31, and the designative volumes (DV)of the magnetic material shims 40 are designated in correspondence withthe respective designative positions (DP).

Each of the plurality of shim supports 31 is configured as shown in FIG.3. As seen from FIG. 3, each shim support 31 includes a shim tray 32, apair of support end portions 34, and a shim holder 38. The shim tray 32is configured of a belt-like body having a rectangular cross-section,and it extends to be elongate rectilinearly. The pair of support endportions 34 are configured unitarily with the shim tray 32, at both theend parts of the shim tray 32. The shim tray 32 and the support endportions 34 are unitarily made of a resin being a nonmagnetic material.Also the shim holder 38 is made of a resin being a nonmagnetic material.

The pair of support end portions 34 are unitarily formed with mountingplates 35, respectively. The shim support 31 is fixed to thepredetermined position (PP) of the inner peripheral surface of thesuperconducting magnet 20 with a screw, not shown, by utilizing mountingholes 35 a respectively formed in the pair of mounting plates 35. Eachshim support 31 is fixed to the superconducting magnet 20 in such amanner that the rear surface 32 a of the shim tray 32 touches the innerperipheral surface of the superconducting magnet 20. At thepredetermined position (PP), the pair of mounting plates 35 arerespectively located at both the end parts of the inner peripheralsurface of the superconducting magnet 20, and the shim support 31touches the inner peripheral surface of the superconducting magnet 20over the full length L thereof.

In the front surface 32 b of the shim tray 32, a plurality of shimpockets 33 are formed at equal intervals along the extending directionof this shim tray. The magnetic material shims 40 of the designativevolume (DV) are accommodated in the shim pocket 33 corresponding to thedesignative position (DP), among the plurality of shim pockets 33. Themagnetic material shims 40 are thin magnetic plates in a numbercorresponding to the designative volume (DV), and they are accommodatedin the shim pocket 33 corresponding to the designative position (DP),together with thin shim spacers 41 made of a nonmagnetic material. Thethin magnetic plates to constitute the magnetic material shims 40 areselected from among thin magnetic plates which are all equal in size andwhich have a plurality of sorts of thicknesses, and that number ofmagnetic plates which corresponds to the designative volume (DV) areselected. The shim spacers 41 are constituted by combining a requirednumber of nonmagnetic plates each of which is equal in size to themagnetic material shim 40. The shim holder 38 covers the shim pocket 33in which the magnetic material shims 40 and the shim spacers 41 areaccommodated, and it holds the magnetic material shims 40 and the shimspacers 41. The shim holder 38 has both its end parts inserted intomounting holes 33 a which correspond to the shim pocket 33 of the shimsupport 31, and it is thus mounted on the shim tray 32. The shim spacers41 press the magnetic material shims 40 in the shim pocket 33 coveredwith the shim holder 38, thereby to restrain the magnetic material shims40 from moving within the shim pocket 33.

Each of the pair of support end portions 34 of the shim support 31 isformed with a connecting hole 34 a and a connection pin inserting hole34 b, and a connection pin 36 is inserted into the connection pininserting hole 34 b. In case of adjusting the magnetic field strength ofthe static magnetic field M, a shim support guide jig 50 is connected tothe designated shim support 31 for which the arrangement and adjustmentof the magnetic material shims 40 need to be performed, by using theconnecting holes 34 a, the connection pin inserting holes 34 b and theconnection pins 36. The shim support 31 to which the shim support guidejig 50 is connected, is designated on the basis of the distributionevaluation of the magnetic field strengths of the static magnetic fieldM.

As shown in FIG. 2, the shim support guide jig 50 includes a shimsupport guide pipe 51, a guide pipe fixing seat 53, a shim supportconnecting rod 54, a fixing lid 56 and a manipulating nut 57. This shimsupport guide jig 50 is used in the state where the superconductingmagnet 20 has generated the static magnetic field M. Therefore, the shimsupport guide pipe 51, the guide pipe fixing seat 53, the shim supportconnecting rod 54, the fixing lid 56 and the manipulating nut 57 whichconstitute the shim support guide jig 50 are made of a nonmagneticmaterial of high rigidity so as not to be attracted by the staticmagnetic field M and to be deformed by the electromagnetic force of thestatic magnetic field M. A stainless steel material, for example,“SUS304”, a glass epoxy resin, or the like is used as the nonmagneticmaterial of the high rigidity.

The shim support guide pipe 51 is a rectangular pipe of length “L1”, andit has an inner guide passage 52 of rectangular section formed byupright side walls 51 s, that are interconnected by a top wall 51 t anda bottom wall 51 u. This shim support guide pipe 51 includes an innerend portion 51 a and an outer end portion 51 b, and the guide passage 52is formed in a manner to be continuous between the inner end portion 51a and the outer end portion 51 b. The guide passage 52 is open in theinner end portion 51 a, and the shim support guide pipe 51 is fixed tothe superconducting magnet 20 by the guide pipe fixing seat 53 so thatthe guide passage 52 may oppose to the designated shim support 31 forwhich the arrangement and adjustment of the magnetic material shims 40are required.

The guide pipe fixing seat 53 is mounted on the outer periphery of theinner end portion 51 a of the shim support guide pipe 51. The guide pipefixing seat 53 is fixed to the inner periphery of the end face of thesuperconducting magnet 20 by employing, for example, a screw or adual-side adhesive tape, thereby to fix the shim support guide pipe 51to the superconducting magnet 20. Owing to the guide pipe fixing seat53, the operation of fixing the shim support guide pipe 51 to thesuperconducting magnet 20 is performed in the state where thesuperconducting magnet 20 has generated the static magnetic field M. Onthis occasion, both the shim support guide pipe 51 and the guide pipefixing seat 53 are made of the nonmagnetic materials, and they are notattracted by the electromagnetic force of the static magnetic field M.Therefore, the shim support guide pipe 51 can be easily fixed to the endpart of the designated shim support 31.

The shim support 31 is inserted into the guide passage 52, and it ispassed through the guide passage 52 and is moved along this guidepassage 52. The guide passage 52 guides the movement of the shim support31. Although the guide passage 52 is a vacant space, it has arectangular cross-section, the size of which is set at a size allowingthe movement of the shim support 31. However, the size of the section ofthe guide passage 52 is adapted to hinder the shim support 31 fromrotating within the guide passage 52, and to hinder the shim holder 38from coming of f during the movement of the shim support 31 within theguide passage 52. When the shim holder 38 comes off during the movementof the shim support 31 along the guide passage 52, the magnetic materialshims 40 accommodated in the shim pocket 33 scatter. Therefore, theguide passage 52 guides the movement of the shim support 31 whilehindering the shim holder 38 from coming off.

The shim support connecting rod 54 is a slender rod of circularcross-section, and the inner end portion 54 a thereof is formed with aconnection pin inserting hole 54 b as shown in FIG. 3. The inner endportion 54 a of the shim support connecting rod 54 is inserted into theconnecting hole 34 a which is formed in one support end portion 34 ofthe shim support 31. In this state, the connection pin 36 is insertedinto both the connection pin inserting hole 34 b and the connection pininserting hole 54 b, whereby the shim support connecting rod 54 isconnected to the shim support 31. The connection pin 36 connects theshim support 31 and the shim support connecting rod 54, and itsimultaneously hinders the shim support connecting rod 54 from rotatingrelative to the shim support 31.

The shim support connecting rod 54 is passed through the guide passage52 of the shim support guide pipe 51, and is connected to the shim tray32 of the shim support 31 by the connection pin 36. Also the operationof connecting the shim support connecting rod 54 and the shim tray 32 isperformed in the state where the superconducting magnet 20 has generatedthe static magnetic field M. Since the shim support connecting rod 54 isalso made of a nonmagnetic material, the electromagnetic force of thestatic magnetic field M does not act on the shim support connecting rod54, and also the connecting operation can be easily executed.

The outer periphery of the shim support connecting rod 54 is formed witha screw 55. The screw 55 is a male screw, which is formed substantiallyover the full length of the shim support connecting rod 54. Concretely,the screw 55 is continuously formed over the full length of the shimsupport connecting rod 54, except the inner end portion 54 a thereof.

The fixing lid 56 is arranged at the outer end portion 51 b of the shimsupport guide pipe 51. This fixing lid 56 is pressed into the shimsupport guide pipe 51 in a manner to close the guide passage 52, at theouter end portion 51 b of the shim support guide pipe 51, thereby to befixed to the shim support guide pipe 51. The manipulating nut 57 isrotatably supported at the inner periphery of the outer end part of thefixing lid 56. The inner periphery of the manipulating nut 57 is formedwith a female screw, and the manipulating nut 57 is threadably engagedwith the screw 55 of the shim support connecting rod 54. Themanipulating nut 57 is manually rotated. However, the manipulating nut57 can also be configured so as to be rotated by employing a motor orthe like drive source.

Since the manipulating nut 57 is rotatably supported by the fixing lid56, this manipulating nut 57 can be rotated in the state where thefixing lid 56 is supported by the outer end portion 51 b of the shimsupport guide pipe 51. Since the manipulating nut 57 is held by thefixing lid 56, the screw 55 is fed on the basis of the rotation of themanipulating nut 57, and the shim support connecting rod 54 is movedalong the extension line thereof, so that the shim support 31 can bemoved together with the shim support connecting rod 54. The manipulatingnut 57 is rotated in the direction of threadably proceeding toward theinner end portion 54 a of the shim support connecting rod 54, wherebythe shim support connecting rod 54 and the shim support 31 are passedthrough the guide passage 52 and are drawn out into the guide passage52. The movements of the shim support connecting rod 54 and the shimsupport 31 are also performed in the state where the superconductingmagnet 20 has generated the static magnetic field M. On this occasion,since the shim support 31 and the shim support connecting rod 54 aremade of nonmagnetic materials, they do not undergo the electromagneticforce from the static magnetic field M, and they can be easily moved.FIG. 4 shows a state where the whole shim support 31 has beenaccommodated in the shim support guide pipe 51 by the rotation of themanipulating nut 57.

In the state shown in FIG. 4, the fixing lid 56 is detached from theshim support guide pipe 51, and the shim support 31 is drawn out fromthe outer end portion 51 b of the shim support guide pipe 51. The lengthL1 of the shim support guide pipe 51 is made greater than the axiallength L of the superconducting magnet 20. The length L of the shimsupport 31 is substantially equal to the axial length L of thesuperconducting magnet 20. Accordingly, the shim support guide pipe 51can accommodate the whole shim support 31 therein.

In addition, the length L1 of the shim support guide pipe 51 is set at alength with which, in the state where the inner end portion 51 a of thisshim support guide pipe 51 is fixed to the superconducting magnet 20,the outer end portion 51 b thereof is hardly influenced by the staticmagnetic field M generated by the superconducting magnet 20. Concretely,the length L1 of the shim support guide pipe 51 is set at about 1.5meters, and the static magnetic field M hardly influences the shimsupport 31 drawn out from the outer end portion 51 b of the shim supportguide pipe 51. The arrangement and adjustment of the magnetic materialshims 40 are performed in a place where the shim support 31 has beendrawn out from the outer end portion 51 b of the shim support guide pipe51. In the arrangement and adjustment of the magnetic material shims 40,the shim holder 38 is detached, and the magnetic material shims 40,which correspond to the designative volume (DV), and the shim spacers 41are accommodated in the shim pocket 33 corresponding to the designativeposition (DP). When the accommodation of the magnetic material shims 40and the shim spacers 41 has been ended, the shim holder 38 is attachedto the shim pocket 33 in which the magnetic material shims 40 and theshim spacers 41 have been accommodated.

After the arrangements and adjustments of the magnetic material shims 40have been completed, the designated shim support 31 is inserted into theguide passage 52 from the outer end portion 51 b of the shim supportguide pipe 51 again. Subsequently to the shim support 31, the shimsupport connecting rod 54 connected thereto is inserted into the guidepassage 52. The manipulating nut 57 held by the fixing lid 56 isthreadably engaged with the shim support connecting rod 54. In a statewhere the fixing lid 56 has been fixed to the outer end portion 51 b ofthe shim support guide pipe 51 again, the manipulating screw 57 isrotated in the direction of threadably coming away from the inner endportion 54 a of the shim support connecting rod 54, whereby the shimsupport connecting rod 54 and the shim support 31 can be moved towardthe superconducting magnet 20. In a state where the shim support 31 hasbeen inserted to the predetermined position (PP) at which the fulllength thereof touches the inner peripheral surface of thesuperconducting magnet 20, this shim support 31 is fixed to the innerperipheral surface of the superconducting magnet 20 by utilizing themounting holes 35 a of the mounting plates 35.

The magnetic field adjustment operation is carried out at an initialadjustment step after the superconducting magnet 20 has been firstassembled into the magnetic resonance imaging equipment 100. Besides, atan inspection adjustment step after the operation of the magneticresonance imaging equipment 100, the magnetic field adjustment operationis carried out if necessary. The initial adjustment step is performed ina state where the magnetic material shims 40 are not accommodated in anyof the shim supports 31 of the magnetic field adjustment device 30. Theinspection adjustment step is performed in a state where the magneticmaterial shims 40 of predetermined volume have been accommodated at thepredetermined position of the predetermined shim support 31. At each ofthe initial adjustment step and the inspection adjustment step, a largenumber of magnetic field measurement means are first arranged in themagnetic field space MC, and the superconducting magnet 20 is thereafterexcited to generate the static magnetic field M. In this state, themagnetic field strength distribution of the magnetic field space MC ismeasured, and the magnetic field uniformity of the distribution isevaluated. The magnetic field uniformity is evaluated in such a way thatany error component is decomposed into a plurality of component terms byemploying a well-known Legendre function expansion.

Concretely, the shim supporter 31 for which the magnetic material shims40 are arranged and adjusted is designated, and the designative position(DP) for accommodating the magnetic material shims 40, and thedesignative volume (DV) corresponding to the designative position aredetermined, on the basis of the evaluation of the magnetic fielduniformity. In the case where the plurality of shim supports 31 aredesignated and where the plurality of designative positions (DP) aredesignated for these shim supports 31, the designative volumes (DV)corresponding to the respective designative positions (DP) aredetermined. In the arrangement of the magnetic material shims 40, thedesignative position (DP) and designative volume (DV) of the magneticmaterial shims 40 are determined so that the respective component termsinto which the error component has been decomposed may be made small,thereby to enhance the magnetic field uniformity. When the volume of themagnetic material shims 40 becomes excessively large, the magnetic fielduniformity changes due to the change of an ambient temperature, and theactual manufacturing errors of the magnetic material shims 40 relativeto the designed computational values thereof cumulate, to incur such adrawback that the magnetic field uniformity lowers. Therefore, thearrangement of the magnetic material shims 40 is determined so as tomake the total volume of the magnetic material shims 40 as small aspossible, and to satisfy any restriction for the total value of therespective component terms into which the error component has beendecomposed in the evaluation of the magnetic field uniformity.

The initial adjustment step is executed in the state where the magneticmaterial shims 40 are not accommodated in any of the shim supports 31.At the initial adjustment step, the arrangement and adjustment of themagnetic material shims 40 are performed for the designated shim support31. Concretely, the shim support guide jig 50 is arranged so as tooppose to the designated shim support 31 in which the magnetic materialshims 40 are not accommodated, and the designated shim support 31 isdrawn out from the outer end portion 51 b of the shim support guide pipe51 through the guide passage 52 by using this shim support guide jig 50.In the arrangement and adjustment of the magnetic material shims 40, theoperation is performed in which the magnetic material shins 40 of thedesignative volume (DV) are accommodated in the shim pocket 33 of thedesignated shim support 31 as corresponds to the designative position(DP). The shim support 31 for which the arrangement and adjustment ofthe magnetic material shims 40 have ended, is inserted into the internalspace 21 at the inner periphery of the superconducting magnet 20,through the guide passage 52 of the shim support guide pipe 51 again,and is fixed to the predetermined position (PP) by using the mountingplates 35.

In a case where, at the initial adjustment step, the arrangement andadjustment of the magnetic material shims 40 are necessary for any othershim support 31 in which the magnetic material shims 40 are notaccommodated, the shim support guide jig 50 is subsequently arranged ata position opposing to the other shim support 31, and the arrangementand adjustment of the magnetic material shims 40 for the other shimsupport 31 are executed likewise to the above. In this way, at theinitial adjustment step, the arrangements and adjustments of themagnetic material shims 40 are performed for all the shim supports 31 inwhich the magnetic material shims 40 need to be accommodated, by usingthe shim support guide jig 50 and in the state where the superconductingmagnet 20 generates the static magnetic field M.

Besides, at the inspection adjustment step, the arrangement andadjustment of the magnetic material shims 40 are performed so as tocorrespond to the determined arrangement of the magnetic material shims40, in other words, to the designative position (DP) and the designativevolume (DV), and the adjustment operation of adjusting at least one ofthe accommodation position and accommodation volume of the magneticmaterial shims 40 is performed. The arrangement and adjustment of themagnetic material shims 40 are performed using the shim support guidejig 50, in the state where the superconducting magnet 20 generates thestatic magnetic field M. That is, the designated shim support 31 isdrawn out, and the magnetic material shims 40 of the designative volume(DV) are accommodated at the designative position (DP), whereupon theshim support 31 is reinserted into the inner periphery of thesuperconducting magnet 20. Accordingly, the deexcitation and subsequentre-excitation of the superconducting magnet 20 need not be performed forthe arrangement and adjustment of the magnetic material shims 40, andthe superconducting magnet 20 continues the state where the staticmagnetic field M is generated.

In a case where, at the inspection adjustment step, the arrangement andadjustment of the magnetic material shims 40 are necessary for any othershim support 31, the shim support guide jig 50 is subsequently arrangedat a position opposing to the other shim support 31, and the arrangementand adjustment of the magnetic material shims 40 for the other shimsupport 31 are executed likewise to the above. At the inspectionadjustment step, the operation of merely removing the magnetic materialshims 40 from the shim support 31 in which the magnetic material shims40 of predetermined volume have been accommodated at a predeterminedposition is also performed on the basis of the distribution evaluationof the magnetic field strengths as may be needed. In this way, thearrangements and adjustments of the magnetic material shims 40 areperformed for all the necessary shim supports 31, by using the shimsupport guide jig 50 and in the state where the superconducting magnet20 generates the static magnetic field M.

When all the arrangements and adjustments of the magnetic material shims40 have been completed, the distribution of the magnetic field strengthsof the magnetic field space MC is measured to confirm the magnetic fielduniformity of the magnetic field space MC again. If no problem exists inthe result of the confirmation, the magnetic field adjustment operationis completed. If, as the result of the confirmation, the arrangement andadjustment of the magnetic material shims 40 are further judged to benecessary, they are repeated again by using the shim support guide jig50. When the magnetic field adjustment operation has been completed, themagnetic field space MC in which the uniformity of the magnetic fieldstrengths is high is attained, the shim support guide jig 50 is detachedfrom the superconducting magnet 20, and the magnetic field generationapparatus 10 of the magnetic resonance imaging equipment 100 is run inthe state where the shim support guide jig 50 has been detached. In therunning state of the magnetic field generation apparatus 10, thedesignated shim support 31 of the magnetic field adjustment device 30corrects the static magnetic field M generated by the superconductingmagnet 20, and the uniform magnetic field required of the magnetic fieldspace MC is generated.

Owing to the use of the shim support guide jig 50 in Embodiment 1, inthe state where the superconducting magnet 20 has generated the magneticfield in the internal space 21, it is possible to draw out thedesignated shim support 31 from the internal space 21 to a place wherethe influence of the magnetic field becomes little, to perform thearrangement and adjustment of the magnetic material shims 40 for thedesignated shim support 31 in the place so as to accommodate themagnetic material shims 40 of the designative volume (DV) at thedesignative position (DP), and to insert the designated shim support 31into the internal space 21. Therefore, in the state where thesuperconducting magnet 20 has generated the static magnetic field M, thearrangement and adjustment of the magnetic material shims 40 can beperformed, and a time period required for the magnetic field adjustmentcan be shortened. Moreover, in the arrangement and adjustment of themagnetic material shims 40, the deexcitation and re-excitation of thesuperconducting magnet 20 are dispensed with, and the liquid helium canbe prevented from decreasing due to its vaporization.

Besides, in the magnetic field generation apparatus 10 in Embodiment 1,at least one designated shim support 31 among the plurality of shimsupports 31 is subjected to the arrangement and adjustment of themagnetic material shims 40 in the state where it has been drawn out fromthe internal space 21 through the guide passage 52 formed inside theshim support guide pipe 51 of the shim support guide jig 50, and it isthereafter inserted into the internal space 21 through the guide passage52. In this manner, the arrangement and adjustment of the magneticmaterial shims 40 are performed in the state where the superconductingmagnet 20 has generated the magnetic field, so that a time periodrequired for the magnetic field adjustment can be shortened. Moreover,in the arrangement and adjustment of the magnetic material shims 40, thedeexcitation and re-excitation of the superconducting magnet 20 aredispensed with, and the liquid helium can be prevented from decreasingdue to its vaporization.

Besides, the magnetic resonance imaging equipment 100 in Embodiment 1includes the magnetic field generation apparatus 10 in Embodiment 1, andit makes the magnetic resonance imaging diagnosis of the patientarranged in the internal space 21. The magnetic field adjustment of themagnetic resonance imaging equipment 100 can be performed in the statewhere the superconducting magnet 20 has generated the magnetic field,and a time period required for the magnetic field adjustment can beshortened. Moreover, in the arrangement and adjustment of the magneticmaterial shims 40, the deexcitation and re-excitation of thesuperconducting magnet 20 are dispensed with, and the liquid helium canbe prevented from decreasing due to its vaporization.

Besides, the magnetic field adjustment method for the magnetic fieldgeneration apparatus 10 in Embodiment 1 includes drawing out thedesignated shim support 31 among the plurality of shim supports 31, fromthe internal space 21 through the guide passage 52 formed inside theshim support guide pipe 51 of the shim support guide jig 50, insertingthe magnetic material shims 40 of the designative volume (DV) into thedesignative position (DP) of the designated shim support 31, andinserting the designated shim support 31 in which the magnetic materialshims 40 have been accommodated, into the internal space 21 through theguide passage 52. According to the magnetic field adjustment method forthe magnetic field generation apparatus 10, in the state where thesuperconducting magnet 20 has generated the magnetic field, the magneticfield adjustment based on the magnetic material shims 40 can beperformed, and a time period required for the magnetic field adjustmentcan be shortened. Moreover, in the arrangement and adjustment of themagnetic material shims 40, the deexcitation and re-excitation of thesuperconducting magnet 20 are dispensed with, and the liquid helium canbe prevented from decreasing due to its vaporization.

Further, the magnetic field adjustment method for the magnetic resonanceimaging equipment 100 in Embodiment 1 is a magnetic field adjustmentmethod for the magnetic resonance imaging equipment 100 which makes themagnetic resonance imaging diagnosis of the patient arranged in theinternal space 21, in which the magnetic field adjustment is performedby employing the magnetic field adjustment method for the magnetic fieldgeneration apparatus 10 in Embodiment 1. According to the magnetic fieldadjustment method for the magnetic resonance imaging equipment 100, inthe state where the superconducting magnet 20 has generated the staticmagnetic field M, the magnetic field adjustment based on the magneticmaterial shims 40 can be performed, and a time period required for themagnetic field adjustment can be shortened. Moreover, in the arrangementand adjustment of the magnetic material shims 40, the deexcitation andre-excitation of the superconducting magnet 20 are dispensed with, andthe liquid helium can be prevented from decreasing due to itsvaporization.

By the way, in the magnetic field generation apparatus 10 of themagnetic resonance imaging equipment 100 in Embodiment 1, the pluralityof shim supports 31 have been assumed to be arranged at thepredetermined positions (PP) of the inner peripheral surface of thesuperconducting magnet 20. It is also possible, however, to arrange acylindrical shim support fixture on the inner peripheral surface of thesuperconducting magnet 20, and to arrange the plurality of shim supports31 on the shim support fixture. Also in this case, the plurality of shimsupports 31 are arranged at the predetermined position (PP) in parallelwith the center axis O-O and at equal peripheral intervals to oneanother. In this case, in the state where the superconducting magnet 20has generated the static magnetic field M, the shim support guide jig 50draws out from the internal space 21, the designated shim support 31among the plurality of shim supports 31 arranged on the shim supportfixture, and it inserts the designated shim support 31 into thepredetermined position (PP) of the shim support fixture again after thearrangement and adjustment of the magnetic material shims 40 have beenperformed.

Embodiment 2

FIG. 5 shows Embodiment 2 of the shim support guide jig according tothis invention. The shim support guide jig 50A of Embodiment 2 shown inFIG. 5 is used instead of the shim support guide jig 50 of Embodiment 1when the magnetic field adjustment of the magnetic field generationapparatus 10 is performed.

As compared with the shim support guide jig 50 of Embodiment 1 shown inFIG. 2, the shim support guide jig 50A of Embodiment 2 has removed thefixing lid 56 and the manipulating nut 57 in Embodiment 1, and it uses amanipulating gear 61 replacing the manipulating nut 57. A manipulatinghandle 62 is added to the manipulating gear 61, and it is connected tothe manipulating gear 61 through pulleys 63 and 64 and a belt 65. Themanipulating gear 61 is a worm gear which meshes with the screw 55 of ashim support connecting rod 54, and it is installed in the outer endportion 51 b of a shim support guide pipe 51. This worm gear is notdriven even when the large force of a shim support 31 has acted thereon.The manipulating gear 61 is arranged in parallel with the shim supportconnecting rod 54. The pulley 63 is coaxial with the manipulating gear61, and the pulley 64 is coaxial with the manipulating handle 62. Theremaining configuration is the same as in the shim support guide jig 50of Embodiment 1.

The shim support 31 which is used in combination with the shim supportguide jig 50A of Embodiment 2, has the same configuration as that of theshim support 31 shown in FIG. 3. The shim support connecting rod 54 isconnected to one support end portion 34 of the shim support 31 by usingthe connection pin 36. The connection pin 36 connects the shim tray 32and the shim support connecting rod 54, and prevents the shim supportconnecting rod 54 from rotating relative to the shim tray 32.

Likewise to the shim support guide jig 50 of Embodiment 1, the shimsupport guide jig 50A of Embodiment 2 is fixed to the inner periphery ofthe end part of the superconducting magnet 20 by the guide pipe fixingseat 53 so as to oppose to the designated shim support 31, in case ofperforming a magnetic field adjustment in the state where thesuperconducting magnet 20 has generated the static magnetic field M.With the shim support guide jig 50A, the manipulating handle 62 ismanually rotated, thereby to drive the manipulating gear 61 and to movethe shim support connecting rod 54. Thus, the designated shim support 31can be drawn out through the guide passage 52.

With the shim support guide jig 50A of Embodiment 2, the shim tray 32abuts against the manipulating gear 61 in a state where the wholedesignated shim support 31 has been drawn out into the guide passage 52of the shim support guide pipe 51. In the state where the shim tray 32abuts against the manipulating gear 61, the guide pipe fixing seat 53 isdetached from the superconducting magnet 20, the shim support guide pipe51 is moved to a place where the static magnetic field M influenceslittle, and the shim support 31 is pulled out from the inner end portion51 a of the shim support guide pipe 51. Incidentally, when the shimsupport 31 is pulled out of the shim support guide pipe 51, theconnection pin 36 needs to be detached. In this regard, the connectionpin 36 can be easily detached by forming a connection pin taking-outwindow, not shown, in the vicinity of the manipulating gear 61 of theshim support guide pipe 51.

In the state where the designated shim support 31 has been taken out ofthe shim support guide pipe 51, the arrangement and adjustment of themagnetic material shims 40 are performed in the place of the littleinfluence of the static magnetic field M. Thereafter, the shim support31 for which the arrangement and adjustment of the magnetic materialshims 40 have been ended is inserted from the inner end portion 51 ainto the shim support guide pipe 51 again, and this shim support guidepipe 51 is fixed again to a position corresponding to a position wherethe designated shim support 31 was fixed by the guide pipe fixing seat53. After the shim support 31 has been connected with the shim supportconnecting rod 54 by the connection pin 36, the manipulating handle 62is manually rotated, thereby to feed the shim support connecting rod 54,to insert the shim support 31 into the internal space 21 and to fix thisshim support 31 to the predetermined position (PP).

By the way, in the shim support guide jig 50A of Embodiment 2, themanipulating handle 62 can also be rotated by a motor or the like drivesource without being manually manipulated. It is also possible that thescrew 55 at the outer periphery of the shim support connecting rod 54 isreplaced with a rack which is formed by arraying a large number ofteeth, and that the manipulating gear 61 is correspondingly replacedwith a pinion which meshes with the rack.

Owing to the use of the shim support guide jig 50A of Embodiment 2,likewise to the shim support guide jig 50 of Embodiment 1, it ispermitted in the state where the superconducting magnet 20 has generatedthe magnetic field in the internal space 21, to draw out the designatedshim support 31 from the internal space 21 to the place where theinfluence of the magnetic field becomes little, to perform thearrangement and adjustment of the magnetic material shims 40 for thedesignated shim support 31 in the place so as to accommodate themagnetic material shims 40 of the designative volume (DV) at thedesignative position (DP), and to insert the designated shim support 31into the internal space 21. Therefore, in the state where thesuperconducting magnet 20 has generated the magnetic field, thearrangement and adjustment of the magnetic material shims 40 can beperformed, and a time period required for the magnetic field adjustmentcan be shortened. Moreover, in the arrangement and adjustment of themagnetic material shims 40, the deexcitation and re-excitation of thesuperconducting magnet 20 are dispensed with, and the liquid helium canbe prevented from decreasing due to its vaporization.

Embodiment 3

FIG. 6 shows Embodiment 3 of the shim support guide jig according tothis invention, while FIG. 7 shows a shim support which is used incombination with the shim support guide jig of Embodiment 3. The shimsupport guide jig 50B of Embodiment 3 shown in FIG. 6 is used instead ofthe shim support guide jig 50 of Embodiment 1, and the shim support 31Bshown in FIG. 7 is used instead of the shim support 31 of Embodiment 1.A plurality of shim supports 31B as shown in FIG. 7 are prepared, andthey are arranged on the inner peripheral surface of a superconductingmagnet 20, in parallel with a center axis O-O and at equal peripheralintervals.

As shown in FIG. 6, the shim support guide jig 50B of Embodiment 3 issuch that a fixing lid 71 is detachably fixed to an outer end portion 51b, that a shim support connecting rod 54 is arranged so as to penetratethrough the fixing lid 71, and that the outer periphery of the shimsupport connecting rod 54 is formed with a screw 55 in a manner to becontinuous over the full length thereof. A manipulating handle 72 forrotating the shim support connecting rod 54 is arranged outside thefixing lid 71. The manipulating nut 57 as in the shim support guide jig50 of Embodiment 1 is not arranged on the fixing lid 71. The remainingconfiguration is the same as in the shim support guide jig 50 ofEmbodiment 1.

As shown in FIG. 7, the shim support 31B which is used in combinationwith the shim support guide jig 50B includes a connector 43 in onesupport end portion 34. The connector 43 is formed in a manner toprotrude on the front surface side of one support end portion 34. Thisconnector 43 is made of a resin being a nonmagnetic material, unitarilywith one support end portion 34. A screw hole 43 a which extends in adirection parallel to the shim support connecting rod 54 is formed inthe connector 43, and a female screw 44 with which the screw 55 at theouter periphery of the shim support connecting rod 54 is threadablyengaged is formed in the connecting hole 43 a. Except these points, theshim support 31B has the same configuration as that of the shim support31 shown in FIG. 3.

Also the shim support guide jig 50B of Embodiment 3 is fixed to aposition opposing to the designated shim support 31B, by the guide pipefixing seat 53, in the state where the superconducting magnet 20 hasgenerated the static magnetic field M. In the state where the shimsupport guide jig 50B is fixed, the manipulating handle 72 is manuallyrotated. Thus, the screw 55 of the shim support connecting rod 54 isthreadably engaged with the female screw 44 formed in the connector 43of the shim support 31B, thereby to connect the shim support connectingrod 54 and the shim support 31B. In this state, the manipulating handle72 is further rotated, whereby the designated shim support 31B can bedrawn out from the internal space 21 through the guide passage 52 of theshim support guide pipe 51.

When the fixing lid 71 is detached from the shim support guide pipe 51,the shim support 31B drawn out into the guide passage 52 is taken outfrom the outer end portion 51 b in a state where it is connected withthe shim support connecting rod 54. The outer end portion 51 b of theshim support guide pipe 51 is located in a place where the influence ofthe static magnetic field M is little, and the arrangement andadjustment of the magnetic material shims 40 are performed in the placeof the little influence of the static magnetic field M. Thereafter, theshim support 31B for which the arrangement and adjustment of themagnetic material shims 40 have been ended is inserted from the outerend portion 51 b into the shim support guide pipe 51 again in the statewhere it is connected with the shim support connecting rod 54, and thefixing lid 71 is fixed to the outer end portion 51 b. In this state, themanipulating handle 72 is manually rotated, thereby to feed the shimsupport connecting rod 54, to insert the shim support 31B into theinternal space 21 and to fix this shim support 31B to the predeterminedposition (PP).

By the way, in the shim support guide jig 50B of Embodiment 3, the shimsupport connecting rod 54 can also be rotated by a motor or the likedrive source without manually manipulating the manipulating handle 72.

Owing to the use of the shim support guide jig 50B of Embodiment 3,likewise to the shim support guide jig 50 of Embodiment 1, it ispermitted in the state where the superconducting magnet 20 has generatedthe magnetic field in the internal space 21, to draw out the designatedshim support 31B from the internal space 21 to the place where theinfluence of the magnetic field becomes little, to perform thearrangement and adjustment of the magnetic material shims 40 in theplace so as to accommodate the magnetic material shims 40 of thedesignative volume (DV) at the designative position (DP) in thedesignated shim support 31B, and to insert the designated shim support31B into the internal space 21. Therefore, in the state where thesuperconducting magnet 20 has generated the magnetic field, thearrangement and adjustment of the magnetic material shims 40 can beperformed, and a time period required for the magnetic field adjustmentcan be shortened. Moreover, in the arrangement and adjustment of themagnetic material shims 40, the deexcitation and re-excitation of thesuperconducting magnet 20 are dispensed with, and the liquid helium canbe prevented from decreasing due to its vaporization.

Embodiment 4

FIG. 8 shows Embodiment 4 of the shim support guide jig according tothis invention. The shim support guide jig 50C shown in FIG. 8 is usedinstead of the shim support guide jig 50 of Embodiment 1.

As shown in FIG. 8, the shim support guide jig 50C of Embodiment 4 issuch that a wire mechanism 80 is included, and that a shim support 31 ismoved through the guide passage 52 of a shim support guide pipe 51 bymanipulating the wire mechanism 80. In the shim support guide jig 50C ofEmbodiment 4, a screw 55 is not formed at the outer periphery of a shimsupport connecting rod 54, and the fixing lid 56 and the manipulatingnut 57 in the shim support guide jig 50 of Embodiment 1 are removed.Except these points, the shim support guide jig 50C has the sameconfiguration as that of the shim support guide jig 50 of Embodiment 1.The shim support 31 has the same configuration as in Embodiment 1, andit is connected with the shim support connecting rod 54 by using theconnection pin 36.

The wire mechanism 80 includes two wires 81 and 82, wire fixtures 83 and84 which fix the respective wires 81 and 82 to the shim supportconnecting rod 54, and a reel 85 which winds the wires 81 and 82. Thewire fixtures 83 and 84 are fixed to the shim support connecting rod 54.The wire fixture 83 is fixed to a position near the inner end portion 54a of the shim support connecting rod 54, and one end of the wire 81 isfixed to this wire fixture 83. The wire fixture 84 is fixed to aposition near the outer end portion 54 c of the shim support connectingrod 54, and one end of the wire 82 is fixed to the wire fixture 84. Thereel 85 is arranged outside the shim support guide pipe 51, and thisreel 85 is additionally provided with a manipulating handle 86. The wire81 is wound in the direction of an arrow n by the reel 85 via pulleys 87a and 87 b, and the wire 82 is wound in a direction opposite to thearrow n by the reel 85 via pulleys 88 a and 88 b.

The reel 85 is rotated by rotating the manipulating handle 86, wherebythe shim support connecting rod 54 and the shim support 31 connectedthereto are moved. When the reel 85 is rotated in the direction of thearrow n by the manipulating handle 86, the wire 81 is taken up on thereel 85 in the direction of the arrow n, and the wire 82 issimultaneously delivered. Owing to this manipulation, the shim supportconnecting rod 54 can be drawn out from the inner end portion 51 a ofthe shim support guide pipe 51 toward the outer end portion 51 bthereof. Besides, when the reel 85 is rotated in the direction oppositeto the arrow n by the manipulating handle 86, the wire 82 is taken up onthe reel 85 in the direction opposite to the arrow n, and the wire 81 issimultaneously delivered. Owing to this manipulation, the shim supportconnecting rod 54 can be inserted from the outer end portion 51 b of theshim support guide pipe 51 toward the inner end portion 51 a thereof.

Also the shim support guide jig 50C of Embodiment 4 is fixed to aposition opposing to the designated shim support 31, by the guide pipefixing seat 53, in the state where the superconducting magnet 20 hasgenerated the static magnetic field M. In the state where the shimsupport guide jig 50C is fixed, the manipulating handle 86 is manuallyrotated to rotate the reel 85 in the direction of the arrow n. Thus, thedesignated shim support 31 can be drawn out from the internal space 21through the guide passage 52 of the shim support guide pipe 51.

The shim support 31 drawn out into the guide passage 52 is taken outfrom the outer end portion 51 b in a state where it is connected withthe shim support connecting rod 54. The outer end portion 51 b of theshim support guide pipe 51 is located in a place where the influence ofthe static magnetic field M is little, and the arrangement andadjustment of the magnetic material shims 40 are performed in the placeof the little influence of the static magnetic field M. Thereafter, theshim support 31 for which the arrangement and adjustment of the magneticmaterial shims 40 have been ended is inserted from the outer end portion51 b into the shim support guide pipe 51 again in the state where it isconnected with the shim support connecting rod 54. In this state, themanipulating handle 86 is manually rotated to rotate the reel 85 in thedirection opposite to the arrow n. Thus, the shim support connecting rod54 is fed so as to insert the shim support 31 into the internal space 21and to fix this shim support 31 to the predetermined position (PP).

By the way, in the shim support guide jig 50C of Embodiment 4, the reel85 can also be rotated by a motor or the like drive source withoutmanually manipulating the manipulating handle 86.

Owing to the use of the shim support guide jig 50C of Embodiment 4,likewise to the shim support guide jig 50 of Embodiment 1, it ispermitted in the state where the superconducting magnet 20 has generatedthe magnetic field in the internal space 21, to draw out the designatedshim support 31 from the internal space 21 to the place where theinfluence of the magnetic field becomes little, to perform thearrangement and adjustment of the magnetic material shims 40 in theplace so as to accommodate the magnetic material shims 40 of thedesignative volume (DV) at the designative position (DP) in thedesignated shim support 31, and to insert the designated shim support 31into the internal space 21. Therefore, in the state where thesuperconducting magnet 20 has generated the magnetic field, thearrangement and adjustment of the magnetic material shims 40 can beperformed, and a time period required for the magnetic field adjustmentcan be shortened. Moreover, in the arrangement and adjustment of themagnetic material shims 40, the deexcitation and re-excitation of thesuperconducting magnet 20 are dispensed with, and the liquid helium canbe prevented from decreasing due to its vaporization.

Embodiment 5

FIGS. 9( a) and 9(b) show Embodiment 5 of the shim support guide jigaccording to this invention, and FIG. 9( a) is a sectional view of theshim support guide jig, while FIG. 9( b) is a side view thereof. FIG. 10shows a shim support 31D which is used in combination with the shimsupport guide jig 50D of Embodiment 5. The shim support guide jig 50D ofEmbodiment 5 shown in FIG. 9( a) (b) is used instead of the shim supportguide jig 50 of Embodiment 1, and the shim support 31D shown in FIG. 10is used instead of the shim support 31 of Embodiment 1. A plurality ofshim supports 31D as shown in FIG. 10 are prepared, and they are fixedto predetermined positions (PP) at equal peripheral intervals and inparallel with a center axis O-O, on the inner peripheral surface of asuperconducting magnet 20.

The shim support guide jig 50D of Embodiment 5 includes a cylindricalshim support guide pipe 51D. A female screw 90 is formed at the outerperiphery of the guide passage 52 of the shim support guide pipe 51D.The female screw 90 is formed at the inner periphery of the shim supportguide pipe 51D in a manner to be continuous from the inner end portion51 a of the shim support guide pipe 51D to the outer end portion 51 bthereof. In the shim support guide jig 50D, the shim support connectingrod 54, fixing lid 56 and manipulating nut 57 in the shim support guidejig 50 of Embodiment 1 are removed. A guide pipe fixing seat 53 is fixedto the outer periphery of the inner end portion 51 a of the shim supportguide pipe 51D. When a magnetic field adjustment is performed, the shimsupport guide pipe 51D is fixed to the superconducting magnet 20 at aposition opposing to the designated shim support 31D, by the guide pipefixing seat 53.

As shown in FIG. 10, the shim support 31D is configured in the shape ofa circular cylinder, the outer periphery of which is formed with a screw45. The screw 45 is formed in a manner to be continuous over the fulllength of the shim support 31D. The shim support 31D is divided into apair of semicylindrical support elements 31 a and 31 b, which areconnected to each other by employing, for example, a hinge. The shimsupport 31D can assume two states; a closed state where the supportelements 31 a and 31 b are closed to each other, and an open state wherethey are opened from each other. The shim support 31D is held in theclosed state in the state where it is fixed to the predeterminedposition (PP) of the inner peripheral surface of the superconductingmagnet 20, and in a state where it is moved. This shim support 31D isheld in the open state when the arrangement and adjustment of magneticmaterial shims 40 are performed. A plurality of manipulating holes 46into which a manipulating rod for manipulating the shim support 31D isfitted are formed in one end part of the shim support 31D.

The shim support 31D is formed with a plurality of shim pockets 33 inthe extension direction thereof. Each shim pocket 33 is configured of apocket 33 a formed in the support element 31 a, and a pocket 33 b formedin the support element 31 b. These pockets 33 a and 33 b are formed inopposition to each other. The magnetic material shims 40 and shimspacers 41 of nonmagnetic material are accommodated in the shim pocket33 corresponding to a designative position (DP). The magnetic materialshims 40 have a designative volume (DV), and they are accommodated inthe pocket 33 a. The shim spacers 41 are accommodated in the pocket 33b, and they press and hold the magnetic material shims 40 when thesupport elements 31 a and 31 b are held in the closed state.

Also the shim support guide jig 50D of Embodiment 5 is fixed to theposition opposing to the designated shim support 31D, by the guide pipefixing seat 53, in a state where the superconducting magnet 20 hasgenerated a static magnetic field M. In the state where the shim supportguide jig 50D is fixed, the manipulating rod not shown is passed throughthe guide passage 52 of the shim support guide pipe 51D, thismanipulating rod is fitted into the manipulating holes 46 of the shimsupport 31D held in the closed state, and the screw 45 at the outerperiphery of the shim support 31D is threadably engaged with the femalescrew 90 of the shim support guide pipe 51D. In this state, the shimsupport 31D is rotated by the manipulating rod. Thus, the designatedshim support 31D can be drawn out from the internal space 21 of thesuperconducting magnet 20 through the guide passage 52 of the shimsupport guide pipe 51D.

The shim support 31D drawn out into the guide passage 52 is taken outfrom the outer end portion 51 b of the shim support guide pipe 51D. Theouter end portion 51 b of the shim support guide pipe 51D is located ina place where the influence of the static magnetic field M is little. Inthe place of the little influence of the static magnetic field M, thesupport elements 31 a and 31 b of the shim support 31D are brought intothe open state, and the arrangement and adjustment of the magneticmaterial shims 40 are performed. Thereafter, the shim support 31D forwhich the arrangement and adjustment of the magnetic material shims 40have been ended and which have been brought into the closed state isinserted from the outer end portion 51 b into the shim support guidepipe 51D again, and the screw 45 of the shim support 31D is threadablyengaged with the female screw 90 of the shim support guide pipe 51D. Inthis state, the shim support 31D is threadably fed by the manipulatingrod. Thus, the shim support 31D is inserted into the internal space 21and is fixed to the predetermined position (PP).

Owing to the use of the shim support guide jig 50D of Embodiment 5,likewise to the shim support guide jig 50 of Embodiment 1, it ispermitted in the state where the superconducting magnet 20 has generatedthe magnetic field in the internal space 21, to draw out the designatedshim support 31D from the internal space 21 to the place where theinfluence of the magnetic field becomes little, to perform thearrangement and adjustment of the magnetic material shims 40 in theplace so as to accommodate the magnetic material shims 40 of thedesignative volume (DV) at the designative position (DP), and to insertthe designated shim support 31D into the internal space 21. Therefore,in the state where the superconducting magnet 20 has generated themagnetic field, the arrangement and adjustment of the magnetic materialshims 40 can be performed, and a time period required for the magneticfield adjustment can be shortened. Moreover, in the arrangement andadjustment of the magnetic material shims 40, the deexcitation andre-excitation of the superconducting magnet 20 are dispensed with, andliquid helium can be prevented from decreasing due to its vaporization.

In the embodiments described above, the magnetic resonance imagingequipment according to this invention is used for making the imagingdiagnosis of a patient. Besides, the magnetic field generation apparatusaccording to this invention can be used for, for example, the magneticresonance imaging equipment. Further, the shim support guide jigaccording to this invention can be used when a magnetic field adjustmentis performed in the magnetic field generation apparatus.

Various modifications and alterations of this invention will be apparentto those skilled in the art without departing from the scope and spiritof this invention, and it should be understood that this invention isnot limited to the illustrative embodiments set forth herein.

1. A shim support guide jig configured for a magnetic field generationapparatus that is configured for a magnetic resonance imaging (MRI)environment, including a superconducting magnet which is configured inthe shape of cylinder and which generates a magnetic field in itsinternal space, and a plurality of shim supports which are arranged inthe internal space and which serve to accommodate therein magneticmaterial shims configured for adjusting a magnetic field strength of themagnetic field, wherein: each of the plurality of shim supports includesa shim tray configured for accommodating the magnetic material shim, theshim tray comprising a belt-like body having a rectangularcross-section, and a shim holder in order to maintain the magneticmaterial shim in the shim tray, and wherein the shim tray is made of anonmagnetic material, the shim support guide jig is constructed in orderto draw out the designated shim support from among the plurality of shimsupports in the internal space and constructed in order to insert thedesignated shim support into the internal space while the magnetic fieldis being generated, the shim support guide jig includes a shim supportguide pipe made of nonmagnetic material and having a predeterminedlength, the shim support guide pipe has an outer end, an inner endconfigured to be fixed to the magnetic field generation apparatus inorder to oppose the designated shim support, and a guide passageconfigured for guiding a movement of the shim tray of the designatedshim support, the guide passage is formed on an inner peripheral surfaceof the shim support guide pipe and extends from the outer end to theinner end of the shim support guide pipe in order to draw out the shimtray of the designated shim support from the internal space through theguide passage and in order to insert the shim tray into the internalspace through the guide passage, and the guide passage has, alongsubstantially its entire length, a rectangular cross-sectioncorresponding to that of the shim tray and sized in order to allow themovement of the shim tray within the guide passage and preventingrotation of the shim tray within the guide passage, the rectangularcross-section defined by two upright side walls interconnected by a topwall and a bottom wall.
 2. The shim support guide jig configured for amagnetic field generation apparatus as defined in claim 1, furthercomprising wherein: the shim support guide jig further includes a shimsupport connecting rod and a manipulating member, the shim supportconnecting rod is made of nonmagnetic material, and the shim supportconnecting rod is passed through the guide passage and is connected tothe shim tray of the designated shim support; the manipulating member iscoupled to the shim support connecting rod in order to move the shimsupport connecting rod along the guide passage and wherein thedesignated shim support is drawn out from the internal space and isinserted into the internal space via the guide passage by movement ofthe shim support connecting rod.
 3. The shim support guide jigconfigured for a magnetic field generation apparatus as defined in claim2, wherein: the shim support connecting rod is formed with a screw atits outer periphery; and the manipulating member is a nut which isthreadably engaged with the screw wherein rotation of the nut producesmovement of the rod along the guide passage.
 4. The shim support guidejig configured for a magnetic field generation apparatus as defined inclaim 2, wherein: the shim support connecting rod is formed with a screwat its outer periphery; and the manipulating member is a manipulatinggear which meshes with the screw, wherein rotation of the gear producesmovement of the rod along the guide passage.
 5. The shim support guidejig configured for a magnetic field generation apparatus as defined inclaim 2, wherein the shim support connecting rod is formed with a rackat its outer periphery; and the manipulating member is a pinion whichmeshes with the rack wherein rotation of the pinion produces movement ofthe rod along the guide passage.
 6. The shim support guide jigconfigured for a magnetic field generation apparatus as defined in claim2, wherein: each of the plurality of shim supports is formed with ascrew hole; the shim support connecting rod is formed with a screw atits outer periphery, the screw is threadably engaged with the screw holein the designated shim support; and the manipulating member is a handlewhich rotates the shim support connecting rod in order to move the shimtray along the guide passage.
 7. The shim support guide jig configuredfor a magnetic field generation apparatus as defined in claim 2, whereinthe manipulating member is a wire attached to the shim supportconnecting rod at first and second longitudinally spaced attachmentpoints, and a rotary reel for winding the wire in first and seconddirections, wherein the wire pulls the rod in a first direction at thefirst attachment point when the wire is wound in the first direction,and wherein the wire pulls the rod in a second direction at the secondattachment point when the wire is wound in the second direction.